Spinal rod approximators

ABSTRACT

Spinal rod approximator for seating a stabilizing rod in a rod-receiving portion of a spinal implant and inserting a closure mechanism is provided. In one embodiment, a spinal rod approximator is provided including a body with gripping branches, inserter shaft, threaded collar, and outer sleeve. The cylindrical outer sleeve is disposed about the distal end portion of the body and is movable between a first position and a second position in which the outer sleeve inhibits separation of the gripping branches.

RELATED INVENTION

This application claims priority of U.S. Provisional Application No.60/442,208, filed Jan. 24, 2003, entitled Spinal Rod Approximator, whichis incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to spinal fixation systems, and inparticular to a spinal rod approximator.

BACKGROUND OF THE INVENTION

Spinal fixation devices are used in orthopedic surgery to align and/orfix a desired relationship between adjacent vertebral bodies. Suchdevices typically include a spinal fixation element, such as arelatively rigid fixation rod, that is coupled to adjacent vertebrae byattaching the element to various anchoring devices, such as hooks,bolts, wires, or screws. The rods can have a predetermined contour thathas been designed according to the properties of the target implantationsite, and once installed, the rod holds the vertebrae in a desiredspatial relationship, either until desired healing or spinal fusion hastaken place, or for some longer period of time.

Spinal fixation devices can be anchored to specific portions of thevertebra. Since each vertebra varies in shape and size, a variety ofanchoring devices have been developed to facilitate engagement of aparticular portion of the bone. Pedicle screw assemblies, for example,have a shape and size that is configured to engage pedicle bone. Suchscrews typically include a threaded shank that is adapted to be threadedinto a vertebra, and a head portion having a rod-receiving element,usually in the form of a U-shaped slot formed in the head. A set-screw,plug, cap or similar type of closure mechanism, is used to lock the rodinto the rod-receiving portion of the pedicle screw. In use, the shankportion of each screw is then threaded into a vertebra, and onceproperly positioned, a fixation rod is seated through the rod-receivingportion of each screw and the rod is locked in place by tightening a capor similar type of closure mechanism to securely interconnect each screwand the fixation rod. Other anchoring devices also include hooks andother types of bone screws.

While current spinal fixation systems have proven effective,difficulties have been encountered in mounting rods into therod-receiving portion of various fixation devices. In particular, it canbe difficult to align and seat the rod into the rod receiving portion ofadjacent fixation devices due to the positioning and rigidity of thevertebra into which the fixation device is mounted. Thus, the use of aspinal rod approximator, also referred to as a spinal rod reducer, isoften required in order to grasp the head of the fixation device, andreduce the rod into the rod-receiving portion of the fixation device.

While several rod approximators are known in the art, some tend to bedifficult and very time-consuming to use. Accordingly, there is a needfor an improved rod approximator and methods for seating a spinal rod ina rod-receiving portion of one or more spinal implants.

SUMMARY OF THE INVENTION

The present invention provides tools, medical devices and methods forseating a stabilizing rod in a rod-receiving portion of a spinal implantand inserting a closure mechanism for locking the rod to the spinalimplant.

In one embodiment, the invention is directed to a tool for seating aspinal rod in a rod-receiving portion of a spinal implant. The tool hasa body having a proximal end portion and a distal end portion. Thedistal end includes first and second flexible branches for gripping aspinal implant, such as a screw or hook. An inserter shaft having adistal end adapted to hold a closure mechanism for said implant isslidably received within the body. A threaded collar adapted to couplethe body and inserter shaft such that the inserter shaft forces a spinalrod into the rod-receiving portion of the spinal implant. An outersleeve is rotatably and slidably mounted onto the distal end of thebody. The sleeve is movable between a first and second position whereinmovement of the sleeve prevents the branches from spreading andseparating from its grip on the implant.

In another embodiment the invention is directed to a method of seating arod into a rod-receiving portion of a spinal implant. The steps includeholding a tool having a body including first and second flexiblebranches for gripping the spinal implant, an inserter shaft slidablyreceived within the body, the inserter shaft having a distal end adaptedto hold a closure mechanism for the implant, and a threaded collar,adapted to couple the body and the inserter shaft. The operator slidesthe inserter shaft beyond the distal end of the body and attaches theclosure mechanism. The closure mechanism is withdrawn into the body. Therod is positioned between the branches of the body. The flexiblebranches are expanded over the implant to securely grip the implant. Thethreaded collar is threaded onto the body advancing the inserter shaftand urging the rod into the implant. The inserter shaft is rotated tolock the closure mechanism to the spinal implant.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is perspective view illustration of an assembled spinal rodapproximator according to one embodiment of the present invention;

FIG. 2 is an exploded view illustration of the components that areassembled to form the device shown in FIG. 1;

FIG. 3 is a perspective view illustration of the device shown in FIG. 1gripping a spinal implant and a spinal rod;

FIG. 4 is a perspective view illustration of the body of the deviceshown in FIG. 1;

FIG. 5A is a side view illustration of the body shown in FIG. 4;

FIG. 5B is a cross-sectional view illustration of the body shown in FIG.4 taken from the distal end;

FIG. 6 is a perspective view illustration of the inserter shaft of thedevice shown in FIG. 1;

FIG. 6A is a cross-sectional view illustration of the inserter shaftshown in FIG. 6;

FIG. 7 is a perspective view illustration of the threaded collar of thedevice shown in FIG. 1;

FIG. 7A is a cross-sectional view illustration of the threaded collarshown in FIG. 7;

FIG. 8 is a perspective view illustration of the outer sleeve of thedevice shown in FIG. 1;

FIG. 9 is a perspective view illustration of the T-handle of the deviceshown in FIG. 1; and

FIGS. 10A and 10B are perspective illustrations of a typical spinalimplant.

DETAILED DESCRIPTION OF THE INVENTION

In general, the present invention provides a spinal rod approximator forseating a stabilizing rod in a rod-receiving portion of a spinalimplant. Typical spinal implants include pedicle screws (monoaxial andpolyaxial), hooks, and other bone screws. The spinal rod approximator ofthe present invention is particularly effective in that it is easy touse, does not require significant force to operate, and is efficient,thereby reducing the time and expense necessary to perform spinalsurgery.

In one embodiment, a rod approximator device is provided including abody for gripping the spinal implant, an inserter shaft for insertingthe closure mechanism and seating the rod into the rod-receiving portionof the spinal implant, and a threaded collar for coupling the movementsof the body and the inserter shaft. The device also includes an outersleeve for locking the body to the spinal implant. The body has agripping means located at its distal end effective to engage a spinalimplant from the side or above. The inserter shaft fits within theinterior channel of the body and is of sufficient length to extendbeyond the body at the proximal and distal ends. The distal end of theinserter is adapted to grasp the closure mechanism. The outer sleeve isrotatably mounted around the outside of the body and is capable ofsliding in a longitudinal direction along the axis of the body toprevent the gripping means from releasing the spinal implant during useof the tool.

The threaded collar couples the body and the inserter shaft such that asthe collar is threaded along the body it pushes on the inserter shaftmoving it through the body. The force generated by the threaded collaris effective to move the inserter shaft with the closure mechanism intocontact with the rod and urge the rod into the rod-receiving portion ofthe spinal implant. Once the rod is seated into the spinal implant, theclosure mechanism is locked into place by rotating the inserter shaft.

FIG. 1 illustrates the preferred embodiment of an assembled spinal rodapproximator 10 that is effective to engage and seat a stabilizing rodin a rod-receiving portion of a spinal implant. FIG. 2 illustrates theindividual components that are assembled to form the spinal rodapproximator. As shown, the tool 10 generally includes a body 20 havinga gripping means 22 on the distal end, an inserter shaft 30 forinserting the closure mechanism, an outer sleeve 40 for preventing thegripping means from releasing from the spinal implant during use, and athreaded collar 50 for coupling the inserter shaft to the body. The toolperforms several actions during its use. As shown in FIG. 3 the tool 10holds the closure mechanism of the spinal implant on the distal end ofthe inserter shaft 30 as the gripping means 22 on the body grip the head105 of the spinal implant 100 while capturing the spinal rod R, thethreaded collar 50 advances the inserter shaft 30 to seat the spinal rodinto the rod-receiving portion of the spinal implant, rotation of theT-handle 60 of the inserter shaft inserts the closure mechanism andlocks it into place within the head of the spinal implant. The channel26 on the body allows the user to visualize the steps as they occur fromoutside the surgical site.

A person having ordinary skill in the art will appreciate that while thetools and devices illustrated herein are described for use with spinalsurgery, the tools can be adapted for use with a variety of medicalprocedures.

The body 20 of the rod approximator 10 is shown in more detail in FIGS.4 through 5A. The body 20 can have a variety of shapes and sizes, but ispreferably a generally longitudinal hollow tube having a proximal endportion 24 a and a distal end portion 24 b. The cross-sectional shapeand size of the body 20, as well as the length of the body 20, can varydepending on the intended use. The body 20 should have a lengthsufficient to enable the distal end portion 24 b of the body 20 to beplaced adjacent a surgical site while the proximal end portion 24 a ofthe body 20 remains outside a patient's body. By varying the size andshape, the body 20 can also be adapted for use in minimally invasiveprocedures.

The gripping means 22 include first and second branches 66 a, 66 bextending longitudinally from the distal end portion 24 b of the body 20and terminating in a distal end 68 a, 68 b. Each branch includes aflexible center 64 a, 64 b portion and two rigid side portions 61 a, 62a, 61 b, 62 b. The center portion 64 is integrally formed from narrowslits 28 cut along the longitudinal axis of the distal end portion ofthe body. These slits provide the center portion the flexibility toexpand around the implant head 105 to grip the implant and thus theslits permit branches 66 a and 66 b to be biased to a closed or grippingposition. The center portion 64 forms the longest extension of thebranch 66. Front rigid side portions 61 a, 61 b extend from the distalend portion 24 b of the body along the center portion and terminate adistance from the distal tip of the center portion. The back rigid sideportions 62 a, 62 b also extend from the distal end portion of the bodyand terminate just before the distal end of the center portion. Thefront and back rigid side portions 61, 62 form a substantially U-shapedrecess to accommodate a spinal rod and spinal implant head. The distancefrom the distal end of the center portion 68 to the distal end of thefront rigid side portion 61 is of sufficient length to allow the head ofa spinal implant to pass through the channel to accommodate a sideapproach to gripping the spinal implant with the tool. The back rigidside portions 62 act as a stop to prevent the tool from completelypassing over the spinal implant as the tool is gripping the implant fromthe side.

Preferably the interior surface 67 of each center portion 64 has aprojection 69 for engaging a corresponding recess 103 located on thehead of the spinal implant. Preferably a pin 63 projects from theinterior surface 65 of the front rigid side portion 61. The pin 63 actsas a stop engaging the top surface 109 of the implant to prevent thetool from sliding down over the entire spinal implant when using thetool to grip the implant from above. FIG. 5A shows a cross-sectionalview of the body 20 from the distal end. This view shows the interiorchannel 21 of the body and depicts the placement of the pins 63 andprojections 69.

Each branch 66 a, 66 b can have virtually any shape and size, and thebranches can include several different mating features to facilitategrasping of the implant. As shown, the opposed branches 66 a, 66 b havea generally elongate, rectangular shape and include opposed innersurfaces 67 a, 67 b. The opposed inner surfaces each preferably have thesame inner diameter which is designed to mate with the outer diameter ofthe head of the spinal implant. The projection 69 is located at thedistal end of the inner surface. The distal most end of each centerportion 68 can be rounded to prevent any potential damage to tissuesurrounding the treatment site as the tool is used to grip the spinalimplant. The projections 69 on the center portions and/or the head ofthe spinal implant can also include a variety of mating elements,including tongue-and-groove connections, dovetail connections, etc.

Along the proximal end portion 24 a of the body is a guide mechanismwhich in the preferred embodiment takes the shape of a channel 26 tocontrol the axial translation and rotational orientation of the insertershaft 30 during operation of the instrument. The guide mechanism alsoallows the surgeon to visualize the steps of operation from outside thesurgical site as they occur. The channel runs parallel to thelongitudinal axis of the body. A portion of the channel 27 branches atan angle from the main portion of the channel and reverses direction.This portion of the channel controls the rotational orientation of theshaft with respect to the body and provides for proper alignment of theclosure mechanism when locking to the implant and allows for releasingof the closure mechanism after locking. In the preferred embodiment thisbranch angles away from the main channel at approximately 90 degrees.

The proximal end portion of the body has external threads 29 to matewith the threads of the threaded collar 50. The external threads 29 areillustrated in the side view of the body (FIG. 5) as a dashed line.Between the distal end portion and the proximal end portion of the bodya pin 25 extends outward for engaging the outer sleeve 40.

Referring now to FIG. 6 the inserter shaft 30 is sized to be slidablyreceived within the interior channel 210 f the body 20 and coupled tothe body 20 by the threaded collar 50. The inserter shaft 30 can alsohave a variety of configurations, but is preferably a generallylongitudinal body having a proximal end portion 32 a and a distal endportion 32 b. The length of the inserter shaft 30 can vary, butpreferably the inserter shaft 30 has a length greater than the length ofthe body 20 such that it may extend beyond the distal and proximal endsof the body.

Located on the tip of the distal end portion 32 b of the inserter shaftis the holder 33 for the spinal implant closure mechanism. The holder 33can be adapted to hold the closure mechanism in a variety of ways. Inthe present invention the holder 33 uses a friction fit or press fit tohold the closure mechanism. By way of non-limiting example, the holder33 can include flexible tabs (not shown) formed therein to snap onto theclosure mechanism. A person having ordinary skill in the art willappreciate that virtually any holding technique can be used to engagethe closure with the distal tip of the inserter shaft.

The proximal end portion 32 a of the inserter shaft is connected to aT-handle 60. Located between the proximal and distal ends of theinserter shaft is a transition zone 36 where the shaft transitions to alarger cross-sectional diameter from the distal portion of the shaft. Atthe proximal end of the transition zone is a shoulder 34 which thethreaded collar 50 engages to reduce the spinal rod into therod-receiving portion of the spinal implant. Projecting out from thetransition zone is a pin 35 which is co operable with the channel 26 onthe body 20 to control the axial translation and rotational orientationof the inserter shaft with respect to the body. The pin travels withinthe channel tracking the steps of the inserter shaft 30 as it grasps thespinal implant closure mechanism, pushes against the rod, inserts theclosure mechanism and locks it into place. Since the pin is visiblethrough the channel, the user is able to visualize these steps as theyoccur from outside the surgical site. Along the channel are markingswhich indicate to the user when to perform each of these steps. The toolis assembled with the pin captured within the channel such that theinserter shaft is not removable from the body. The length of the channellimits the distance that the inserter can translate within the body. Thedistance between the channel and the branched portion 27 of the channellimits the amount the inserter can rotate within the body. This distancecorresponds to the amount of rotation necessary to lock the closuremechanism in place.

A person having ordinary skill in the art will appreciate that virtuallyany guiding technique can be used to guide the inserter shaft within thebody. For example, the pin could be located on the body and engage achannel on the inserter shaft.

A projection 38 is located on the surface of the inserter shaft betweenthe proximal end portion and the shoulder. Projection 38 rests againstthe rim 56 at the proximal end of the threaded collar to prevent theinserter shaft from sliding down and extending beyond the distal end ofthe body after the closure mechanism has been picked up and prior togripping to implant.

Referring now to FIG. 7 and FIG. 7A, threaded collar 50 has a hollowbody with internal threads 52 adapted to engage the external threads 29of the body 20. Located within the threaded collar is a central shaft 51having an internal diameter that is greater than the diameter of theproximal portion of the inserter shaft and less than the diameter of theshoulder 34 at the transition zone of the inserter shaft. The centralshaft extends from the proximal end of the threaded collar. The distalrim 54 of the shaft projects beyond the distal end of the collar. Thecollar is rotatable and slidable along the proximal end portion of theinserter shaft 30 up to the transition zone. When the collar is advancedinto contact with the body it is threaded onto the external threads 29of the body 20, such that the distal rim 54 of the center shaft engagesthe shoulder 34 of the inserter shaft 30 to push the closure mechanismheld by the distal end 33 of the inserter shaft against a spinal rod toseat the rod in the rod-receiving portion of the implant.

Referring now to FIG. 8, outer sleeve 40 is a hollow substantiallycylindrical tube defining an interior channel 41 extending therethrough.The interior channel is sized to allow it to slide along the distal endportion 24 b of the body 20 from a first to a second position. In thefirst position the outer sleeve is raised above the flexible centerportion 64 of the branch 66 on the body such that the center portion 64can expand to grip the implant. In the second position the outer sleevelocks the branches to the implant. The distal end of the outer sleevehas opposed U-shaped channels 42 a, 42 b configured to allow the tool 10to capture a spinal rod above the head of the spinal implant whilegripping the implant. The arms 44 a, 44 b located between the U-shapedchannels are adapted to slide over the narrow slits 28 of the flexiblecenter portions 64 a, 64 b when the sleeve is advanced to the secondposition to lock the branches to the implant. Pin 25 extending from thebody projects into a channel 46 on the proximal end portion of the outersleeve to couple the body and outer sleeve. The channel allows the outersleeve to move from a first to a second position.

In use, one or more spinal implants 100 are screwed into vertebral bonestructures. Typically, where two spinal implants 100 are fastened intoadjacent vertebra, a spinal rod is inserted into the rod-receivingportion 107 of each implant. However, due to the alignment of theimplants 100, it can be difficult to position the rod within eachrod-receiving recess 107. Thus, a rod approximator device is necessary.In use, the outer sleeve is raised in the first position as the spinalrod approximator 10 picks up and retains the spinal implant closuremechanism in the distal end portion 24 b of the inserter shaft. The pinon the inserter shaft is visible at the distal end of the channel whenthe inserter shaft is advanced to pick up the closure mechanism. The pintravels back up the channel to the distal end of the channel when theinserter shaft 30 is retracted inside the body 20 above the U-shapedchannels 42 a, 42 b of the outer sleeve. At this position the projection38 rests against the rim 56 of the threaded collar.

The tool 10 approaches the head of the spinal implant from above or theside. The flexible center portions 64 of the branches expand to slideover the implant head and spring back to their original position to gripthe recesses 103 on the outside of the spinal implant head 105. Theouter sleeve 40 slides down into the second position preventing thebranches from spreading and disengaging the grip on the implant. Thethreaded collar 50 is turned to engage the external threads 29 on thebody 20 such that the rim 54 of the threaded collar abuts the shoulder34 of the inserter shaft 30 and advances the shaft. The closuremechanism held in the distal end of the inserter shaft contacts thespinal rod, forcing the rod into the rod-receiving portion 107 of thespinal implant. As the inserter shaft advances axially, the pin followsthe channel until it reaches the portion 27 of the channel that branchesoff at an angle. The pin reaches this position when the rod is seated inthe implant. At this point the closure mechanism is properly aligned andthe T-handle 60 of the inserter shaft is rotated to insert and lock theclosure mechanism into the head of the spinal implant. The insertershaft is pulled up to disengage the closure mechanism from the holdingend and the outer sleeve is slid back to the first position so that thebranches of the body are permitted to expand and disengage from theimplant simply by pulling the device away from the implant.

One of ordinary skill in the art will appreciate further features andadvantages of the invention based on the above-described embodiments.Accordingly, the invention is not to be limited by what has beenparticularly shown and described, except as indicated by the appendedclaims. All publications and references cited herein are expresslyincorporated herein by reference in their entirety.

1. A tool for seating a spinal rod in a rod-receiving portion of aspinal implant, the tool comprising: a body having a proximal endportion and a distal end portion, said distal end portion including afirst and second flexible branch for gripping a spinal implant, saidflexible branches being biased to a closed position, said flexiblebranches being spaced-apart a distance to form a first substantiallyU-shaped recess, said first substantially U-shaped recess opening at anend of the distal end portion and extending proximally from the end; aninserter shaft slidably received within said body, said inserter shafthaving a distal end adapted to hold a closure mechanism for saidimplant; a threaded collar, adapted to couple said body and saidinserter shaft, wherein said inserter shaft forces a spinal rod into therod-receiving portion of said implant; and a substantially cylindricalouter sleeve disposed about the distal end portion of the body andmovable between a first position and a second position in which theouter sleeve surrounds the branches to inhibit separation of the firstand second flexible branches, the outer sleeve including a pair ofspaced-apart arms at a distal end of the outer sleeve, the arms defininga second substantially U-shaped recess, the second substantiallyU-shaped recess aligning with the first substantially U-shaped recesswhen the outer sleeve is in the second position to accommodate a spinalrod within the first substantially U-shaped recess and the secondsubstantially U-shaped recess.
 2. A tool for seating a spinal rod in arod-receiving portion of a spinal implant, the tool comprising: a bodyhaving a proximal and distal end portion, wherein an interior channelextends between the distal and proximal portions, said distal endportion having flexible branches for gripping a spinal implant and saidproximal end portion having external threads, the flexible branchesbeing spaced-apart a distance to form a first substantially U-shapedrecess, the first substantially U-shaped recess opening at an end of thedistal end portion and extending proximally from the end; an insertershaft slidable within said interior channel of the body having aproximal end portion, a distal end portion, and a transition zonelocated between said distal and proximal end portions, said transitionzone having a diameter larger than the proximal end portion, said distalend portion adapted to hold a closure mechanism for the spinal implant;a collar having an internally threaded hollow body and a central shaftattached to said hollow body, wherein said central shaft limitsindependent motion between said inserter shaft and said collar, whereinsaid diameter of the transition zone of the inserter shaft is greaterthan an inner diameter of the central shaft of the collar, said centralshaft of the collar having a distal and a proximal portion, saidproximal portion attached to said hollow body and said distal portionextending past said hollow body and having an abutment surface forengaging the transition zone portion of said inserter shaft; and asubstantially cylindrical outer sleeve disposed about the distal endportion of the body and movable between a first position and a secondposition in which the outer sleeve surrounds the flexible branches toinhibit separation of the branches, the outer sleeve including a pair ofspaced-apart arms at a distal end of the outer sleeve, the arms defininga second substantially U-shaped recess, the second substantiallyU-shaped recess aligning with the first substantially U-shaped recesswhen the outer sleeve is in the second position to accommodate a spinalrod within the first substantially U-shaped recess and the secondsubstantially U-shaped recess.
 3. The tool of claim 2 wherein saidflexible branches are biased in a closed position.
 4. A tool for seatinga spinal rod in a rod-receiving portion of a spinal implant comprising:a body having a proximal and a distal end portion, said distal endportion having branches for gripping a spinal implant, wherein aninterior channel extends between the distal and proximal ends, thebranches being spaced-apart a distance to form a first substantiallyU-shaped recess, the first substantially U-shaped recess opening at anend of the distal end portion and extending proximally from the end; aninserter shaft having a proximal and a distal end portion, said distalend portion adapted to hold a closure mechanism for the spinal implant,wherein said shaft is sized to fit within the interior channel of thebody; a guide mechanism co-operable with said shaft and said bodywhereby said guide mechanism limits an independent movement of the shaftwithin the body, the guide mechanism including a channel and a pinadapted to fit within said channel, the channel located on the body andextending parallel to a longitudinal axis of the body, the pin locatedon said shaft; and a substantially cylindrical outer sleeve disposedabout the distal end portion of the body and movable between a firstposition and a second position in which the outer sleeve surrounds thebranches to inhibit separation of the branches, the outer sleeveincluding a pair of spaced-apart arms at a distal end of the outersleeve, the arms defining a second substantially U-shaped recess, thesecond substantially U-shaped recess aligning with the firstsubstantially U-shaped recess when the outer sleeve is in the secondposition to accommodate a spinal rod within the first substantiallyU-shaped recess and the second substantially U-shaped recess.
 5. Thetool of claim 4 wherein a portion of said channel branches off at anangle and reverses direction.
 6. The tool of claim 5 wherein a pointwhere said channel branches off corresponds to the point where thespinal rod is fully seated in the implant.
 7. The tool of claim 5wherein said angle is approximately 90 degrees.
 8. The tool of claim 4wherein the pin and channel prevent the shaft from being removed fromthe body.
 9. The tool of claim 4 wherein the independent movementlimited is a rotational orientation of the inserter shaft with respectto the body.
 10. The tool of claim 4 wherein the independent movementlimited is an axial translation of the inserter shaft with respect tothe body.